During your post-game quest, you can battle Kōji Nishino at even a tougher challenge. This can be done once a day. His entire team holds Leftovers. Clefable will use Cosmic Power to raise its Defense and Special Defense stats plus Stored Power to inflict more damage the more stats it raises on itself. Azumarill with the ability Huge Power will use Bulldoze to slow opponents down and Superpower for big damage at the expense of its own Attack and Defense stats. Alomomola has a combo of Toxic, Wish, and Protect along with the first striking Aqua Jet. Snorlax will stun opponents by using Yawn or Body Slam. Moves like Brick Break and Thunderbolt would work best for this round. ... https://www.youtube.com/watch?v=IZHE_rFfOwQ

After you venture on all of the Sevii Islands, bringing the Ruby and Sapphire to Celio at the Pokémon Net Center on One Island, one of these legendary Pokémon will roam all over the routes in the Kanto region. If you hear the wild battle music in a higher pitch, that means you have encountered the roaming Pokémon. The roaming Pokémon you encounter is on Level 50 and will flee on the first turn. If you have the Master Ball, it would be the time to use it. If you don’t, have any Pokémon use Mean Look to prevent escape but don’t let the opponent use Roar to force you away from battle. Depending on your starter, only one of these will roam in Kanto. If you started with Bulbasaur, Entei will roam. If you started with Charmander, Suicune will roam. If you start with Squirtle, Raikou will roam. ... https://www.youtube.com/watch?v=CkrUqRyK8sM